Silicon dioxide particles deposited in vessels and cartilage of the femoral head.

Silicosis had been considered for decades as an illness with manifestations of lung fibrosis due to inhalation of overconcentrated SiO₂ dust. To the best of our knowledge, studies have yet to report SiO₂ deposits in any other tissues and organs. In the present case, while performing bilateral artificial total hip arthroplasty for one patient, we found that the articular cartilage of the bilateral femoral head was black. Therefore, specimens thereof were sent for pathological examination. Pathological examination (immunohistochemistry) and polarized light microscopy revealed the presence of considerable brown, acicular, rhombic, and crumb-like crystals. The crystals were mainly composed of SiO₂. SiO₂ could deposit in vessels and femoral head cartilage via blood circulation.